The Aster family isn't quite what it seems

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Among aster enthusiasts, 2015 will be remembered as the year the RHS finally threw in the towel and admitted that there weren’t as many asters as there used to be. In fact, not many at all. To understand how we got here, we need to go right back to the 18th century, when Linnaeus was laying the foundations of our modern Latin binomial names. He picked on the Italian aster as the “type” species of his new Aster genus and called it Aster amellus. In fact, A. amellus became the “type” for not only a genus, but a whole family: the daisy family, previously the Compositae but now normally the Asteraceae.

Linnaeus and other botanists soon noticed that there were quite a few other European plants that looked rather like the Italian aster, so these were added to the new genus. But things really took off when botanists crossed the Atlantic and found more asters than you could shake a stick at, in particular A. novi-belgii, the New York aster, and A. novae-angliae, the New England aster. These two are the plants that are most often called Michaelmas daisies, from their habit of putting on a good show around the feast of St Michael the Archangel on September 29. These days it’s hard to imagine the autumn garden without them.

New England aster, or more commonly known as Michaelmas daisiesCredit:
Alamy

Aster just grew and grew, and at its peak included around 500 species, a global franchise stretching from the Pacific coast of North America to Japan. But suspicions grew that not all those plants belonged together, suspicions that were confirmed in the mid-Nineties when botanists started to look directly at DNA.

It soon became clear not only that the North American asters were unrelated to the European ones, but that many of them weren’t even closely related to each other. Soon species were being hived off into new genera, some of them apparently constructed from a bag of random Scrabble tiles: for example, Eurybia, Xanthisma and Doellingeria. The good news, if you can call it that, is that most of the plants that gardenersmight be interested in were found together in the largest of these new genera.

Michaelmas daisy Credit:
Alamy

The bad news is that the euphonious moniker of that genus is Symphyotrichum (worth practising first before attempting that in public). Thus the New York and New England asters are now Symphyotrichum novi-belgii and S. novae-angliae. Similarly the very pretty and distinctive, and deservedly popular, small-flowered heath aster is now S. ericoides.

The native British flora only ever had a couple of asters, and I’m sorry to say that neither has survived the shake-up. I could tell you what’s happened to them, but trust me, you don’t want to know. Where does that leave Aster, at least as far as gardeners are concerned? Aster amellus, of course, defines the genus, so it’s unchanged. So are a few of its close relatives, including A. alpinus and A. pyrenaeus (both good garden plants), and – best of all – the A. amellus x thomsonii hybrid, A. x frikartii.

But just as you can carry on calling the New Zealand shrubs hebes, even though all of them are now in the genus Veronica, none of this has any effect on the common name “aster”. Nor, thank heavens, is there anything to stop you calling them Michaelmas daisies.